Heater Fan Continually Running

[Koerb]

Went out this morning to check on the rig and was surprised to hear the heater fan running. Thermostat was set at 40 degrees and it hasn't fallen below 60 since returning from our last outing. First tried turning off the thermostat with negative results, then disconnected both the electrical and Battery power. Fan of course shutdown upon battery disconnect but after 15 minutes and reconnecting the battery it continued to run. Was hoping for a reset of some kind but no such luck, anyone ever run into this and if so what is the fix. Thanks for any guidance you might provide.

John Koerber

[dsprik]

John try this procedure on the following thread:

http://www.montanaowners.com/forums/...ad.php?t=29156

Good luck!

*On Edit~ John, I also have the "4 Button Reset" procedure. Let me know if you have the 5 button or 4 button thermostat.

[snfexpress]

When the fan continues to run, it usually indicates a faulty circuit board - they cost about $170. However, I would definitely try Dave's trick, first.

Glenn - do you think it would be a good idea to add the 4- and 5-button reset procedures to the home page?

From a previous post:

There are just a few basic parts to these blasted furnaces.

First, there is the circuit board, which is the easiest to replace. Typically, if the fan is blowing and WON'T turn off unless you either pull the 12v fuse or turn off the unit on top (there is a switch), then it is probably the circuit board.

Second, there is a sail switch. This is a switch inside the fan housing (4 screws to get the fan housing front half off). This switch has a long piece of metal on it about 1/4" wide. As the fan turns, the air pushes against this long thin metal strip and pushes it closed, which activates the switch. The switch is now allowing 12v to go thru it which in turn allows the gas valve to be able to operate.

Third is the electrode. This is a bear to replace (I did it, and it took me an hour to get the old one out and the new one in by wiggling it every which way in a very cramped space). The electrode, if bad, won't "spark" and ignite the gas. If you go to the trouble of getting the unit all the way out and on a bench, then I would take the extra time and replace the electrode.

Fourth is the gas valve. I haven't replaced this valve, and if it ever gets to that point, I'm just going to order a new furnace. Looks too complicated and dangerous, at least to me.

So, in order of price, it goes 1, 4, 3, 2. Roughly $170 for the board and just a few bucks for the sail switch and electrode. Don't know the price of the gas valve.

In order of difficulty, it goes 1, 2, 3, 4.

In order of your problem, I would suggest #3. Let me ask you: Does you furnace ever light? The unit will try 3 times, then "lock out", so you have to turn the unit switch off then back on. When you turn it back on (with the t-stat turned to furnace and calling for heat - set to 99 degrees), the fan should come on, then the ignitor on the circuit board (after about 20 seconds) should go click, click, click and then the propane should be burning. If the propane does not ignite, the exhaust sound will not change, and then the board will try a second and a third time.

Oh, I would try one thing first. Open your stove hood and disconnect the gas to the burners. Fit a gas guage on to the propane supply line. It should read between 10 and 14 inches WC or about 3 lbs of pressure. But, Atwood's manual states that before doing a pressure check, to first disconnect the propane supply and cap this supply line to the furnace. If the pressure is low, go to your regulator and adjust as necessary (under the black cap on the regulator).

Sorry for the long post, and hope that what I wrote makes sense to you. Good Luck!

[dsprik]

quote:Originally posted by snfexpress

When the fan continues to run, it usually indicates a faulty circuit board - they cost about $170.

John, I was going to mention, that as Mike mentioned, another source of the problem was your board. A few MOCers have had to replace these boards. Try the reset first, though.

[dsprik]

Michael, I was thinking the same as you regarding Glenn putting these procedures on the MOC info page...

The five button thermostat reset:
1. Turn slide switch to OFF position.
2. Press and hold MODE (top) and ZONE (bottom) buttons.
3. Turn slide switch to ON position.
4. Release MODE and ZONE buttons.
5. FF appears indication reset is complete.

The four button thermostat reset:
1. Turn all zones OFF.
2. Press and hold temp UP and DOWN buttons together.
3. Press and release MODE button once.
4. Release temp UP and DOWN buttons.
5. Press and release MODE button once again.
6. Thermostat light goes out indicating reset is complete.

[Koerb]

First of all thank you all for your quick responses. After reading your replies I went out to apply the "5 button reset" procedure and the dang fan had stopped running! The thermostat is still in the off position. Prior to my AC/DC power disconnect I did indeed try the furnace startup with positive results, she fired right up and provided warm air. I then brought the set point back down and the furnace shutdown but fan continued to run past it's shutdown period. I will go out later on today and kick on the thermostat and see what happens, keep your fingers crossed for me.

John Koerber

[rogue]

John, I'm sure you know that when you turn down the thermostat, the furnace shuts down, and the fan will continue to run until the air is cool enough, usually 3-5 minutes, then the fan should stop. It will not stop as soon as the furnace does. If it continues to run say after 10 minutes after the furnace stops, then you have a problem.
Bob

[Ozz]

Probably the bi-metal switch is stuck closed.